ASTM D495-2014 pdf free download.Standard Test Method for High-Voltage, Low-Current, Dry Arc Resistance of Solid Electrical Insulation.
ASTM D495-2014 covers, in a preliminary fashion, the differentiation of similar materials’ resistance to the action of a high-voltage, low-current arc close to the surface of insulation, when a conducting path is formed causing the material to become conducting due to the localized thermal and chemical decomposition and erosion.
Referenced Documents
D1711 Terminology Relating to Electrical Insulation;
D2132 Test Method for Dust-and-Fog Tracking and Erosion Resistance of Electrical Insulating Materials;
D2303 Test Methods for Liquid-Contaminant, Inclined-Plane Tracking and Erosion of Insulating Materials;
D3638 Test Method for Comparative Tracking Index of Electrical Insulating Materials;
D6054 Practice for Conditioning Electrical Insulating Materials for Testing;
5. Interferences
5.1 Changes in both the timing of the intermittent arc and the current, as well as other changes affecting the nature of the discharge, can affect the duration of a test of most specimens taken from a group of dissimilar materials. Any of these changes can drastically alter a material’s position in order of rank. Regardless of the conditions of anticipated use, do not USC data obtained by this test method to infer that the materials examined occupy an unchanging quality relationship to each other.
5.2 This test method describes two electrode systems: stainless steel strip and tungsten rod. When testing materials with poor to moderate arc resistance (up to 180 s). use the stainless steel strip electrodes as the preferred technique.
7. Safety Precautions
7.1 Warning—It is possible that lethal voltages will be present during this test. Ills essential that the lest apparatus, and all associated equipment potentially electrically connected to it, be properly designed and installed for safe operation. Solidly ground all electrically conductive parts that any person might come in contact with during the test. Provide means for use at the completion of any test to ground any parts which:
were at high voltage during the test: will potentially have acquired an induced charge during the test; will potentially retain a charge even after disconnection of the voltage source. Thoroughly instruct all operators in the proper way to conduct tests satèly. When making high voltage tests, particularly in compressed gas or in oil, it is possible that the energy released at breakdown will he sufficient to result in fire, explosion, or rupture of the test chamber. Design test equipment, test chambers, and test specimens so as to minimize the possibility of such occurrences and to eliminate the possibility of personal injury.